fallout 3 for pc is excellent. The user made mods are just awesome. I mostly use hi res texture mods, female body replacer mods and mart's mutant mod, which is a must have in my opinion. Some of the dlc is not bad either, although I hear that the ufo dlc is under whleming.
You can view the extensive mods available for pc fallout 3 here:
There are also more mods and discussions of how to use and install some of the more complex ones here at the official forums: